Definition of Soils. 6 1 



" The true nourishment of plants is water and 

 decomposing organic matter. 



"Vegetable or animal matters, when finely di- 

 vided, not only give coherence but likewise softness 

 and penetrability : but neither they nor any other 

 part of the soil must be in too great proportion. 



" A certain degree of friability or looseness of 

 texture is also required in soils, in order that the 

 operations of culture may be easily conducted ; 

 that moisture may have free access to the fibres of 

 the roots ; that heat may be readily conveyed to 

 them ; and that evaporation may proceed without 

 obstruction. These are commonly obtained by the 

 presence of sand. A great proportion of sand, 

 however, always produces sterility. 



" As alumina possesses all the properties of ad- 

 hesiveness in an eminent degree, and silex those 

 of friability, it is obvious that a mixture of these 

 two earths would furnish everything wanted to form 

 the most perfect soil as to water and the operations 

 of culture. 



" The power of soil to absorb water from the air 

 is much connected with fertility ; when this power 

 is great the plant is supplied with moisture in dry 

 seasons. . . . The soils most efficient in supply- 

 ing the plant with water by atmospheric absorption, 

 are those in which there is a due mixture of sand, 

 finely divided clay, and carbonate of lime, with 



